RISC-V: Access CSRs using CSR numbers

We should prefer accessing CSRs using their CSR numbers because:
1. It compiles fine with older toolchains.
2. We can use latest CSR names in #define macro names of CSR numbers
   as-per RISC-V spec.
3. We can access newly added CSRs even if toolchain does not recognize
   newly addes CSRs by name.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

arch/riscv/kernel/smp.c

@@ -95,7 +95,7 @@ void riscv_software_interrupt(void)
 	unsigned long *stats = ipi_data[smp_processor_id()].stats;
 
 	/* Clear pending IPI */
-	csr_clear(sip, SIE_SSIE);
+	csr_clear(CSR_SIP, SIE_SSIE);
 
 	while (true) {
 		unsigned long ops;